2pi4
From Proteopedia
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T7RNAP complexed with a phi10 protein and initiating GTPs.
Overview
DNA-directed RNA polymerases are capable of initiating synthesis of RNA, without primers, the first catalytic stage of initiation is referred to as, de novo RNA synthesis. De novo synthesis is a unique phase in the, transcription cycle where the RNA polymerase binds two nucleotides rather, than a nascent RNA polymer and a single nucleotide. For bacteriophage T7, RNA polymerase, transcription begins with a marked preference for GTP at, the +1 and +2 positions. We determined the crystal structures of T7 RNA, polymerase complexes captured during the de novo RNA synthesis. The DNA, substrates in the structures in the complexes contain a common Phi10, duplex promoter followed by a unique five base single-stranded extension, of template DNA whose sequences varied at positions +1 and +2, thereby, allowing for different pairs of initiating nucleotides GTP, ATP, CTP or, UTP to bind. The structures show that the initiating nucleotides bind RNA, polymerase in locations distinct from those described previously for, elongation complexes. Selection bias in favor of GTP as an initiating, nucleotide is accomplished by shape complementarity, extensive protein, side-chain and strong base-stacking interactions for the guanine moiety in, the enzyme active site. Consequently, an initiating GTP provides the, largest stabilization force for the open promoter conformation.
About this Structure
2PI4 is a Single protein structure of sequence from Bacteriophage t7 with MG and GH3 as ligands. Active as DNA-directed RNA polymerase, with EC number 2.7.7.6 Full crystallographic information is available from OCA.
Reference
Mechanism for de novo RNA synthesis and initiating nucleotide specificity by t7 RNA polymerase., Kennedy WP, Momand JR, Yin YW, J Mol Biol. 2007 Jul 6;370(2):256-68. Epub 2007 Mar 21. PMID:17512007
Page seeded by OCA on Wed Nov 21 13:32:35 2007
